Guide and protector arrangement incorporating fill-up float valve means

ABSTRACT

A guide and protector arrangement for the lower end of a tubular drill string with drilling means thereon which are to be lowered in a well bore including molded jacket means for protecting the drilling means, the jacket means including passage means therein for communicating fluid between the well bore and the interior of the string and fill-up float valve means adapted to be removably positioned within the jacket means for controlling the fluid flow between the well bore and the passage means in the jacket means.

United States Patent [191 Lorenz et al.

[ 1 GUIDE AND PROTECTOR ARRANGEMENT INCORPORATING FILL-UP FLOAT VALVEMEANS Filed:

Inventors: Howard I. Lorenz, Eugene P.

Rosser, both of Houston,,Tex.

Assignee: Nobel Drilling Corporation, Tulsa,

Okla.

Jan. 21, 1971 Appl. No.: 108,449

US. Cl. ..175/307, 175/318, 166/225 Int. Cl. ..E2lb 9/00 Field of Search.......l75/307, 317, 318; 166/225 References Cited UNITED STATES PATENTSSchnitter 166/225 Baker Baker McMahan ..175/307 Primary Examiner-JamesA. Leppink Attorney-Jack W. Hayden [5 7 ABSTRACT A guide and protectorarrangement for the lower end of a tubular drill string with drillingmeans thereon which are to be lowered in a well bore including moldedjacket means for protecting the drilling means, the jacket meansincluding passage means therein for communicating fluid between the wellbore and the interior of the string and fill-up float valve meansadapted to be removably positioned within the jacket means forcontrolling the fluid flow between the well bore and the passage meansin the jacket means.

15 Claims, 7 Drawing Figures PATENTED FEB 2 71975 SHEET 2 OF 2 flan/0rd[0 9/72 fave/7e f. Fairer [NI/EN TOR I Jack W. H0 49 'Hlli Zia ATTORNEYGUIDE AND PROTECTOR ARRANGEMENT INCORPORATING FILL-UP FLOAT VALVE MEANSCROSS REFERENCES TO RELATED APPLICATIONS The present invention relatesto improvements in our copending applications identified as Devices andMethods for Protecting and Guiding Rock Bits filed on June 12, 1969bearing Ser. No. 832,673, now abandoned; and incorporated in Method andArrangement for Protecting and Guiding Drilling Bits filed on Jan. 19,1971, bearing Ser. No. 107,786; and Bit Guide and ProtectorIncorporating an Arrangement for lnitially Inserting or Replacing BitJets" filed on June 1, I971, bearing Ser. No. 148,499.

BACKGROUND OF THE INVENTION The present invention relates to the fieldof art for lowering tubular drill strings which incorporate a drill bitor drilling means thereon into a well bore. In order to reduce the loadand reduce the wear on the brakes, drawworks and the other components ofthe hoisting mechanism of a drilling rig, it is desirable to lower atubular drill string into a well bore in a manner so that, under somecircumstances, it may partially flll to a predesired and predeterminedlevel to thereby float the drill string into the well bore.

Also, due to the out of round tolerances, 1D. and OD. tolerance, as wellas wall thickness tolerance, an offset or misalignment of sections oftubular members such as casing may occur in the well bore, particularlyat the joints where the sections of tubular members or casing areconnected together. Additionally, it is desirable to protect the wallcake on the well bore wall. Therefore, it is desirable to lower atubular drill string into the well bore in a manner so as to inhibitdamage to surrounding casing or tubular member positioned in the wellbore; to inhibit damage to the wall cake of the well bore or to inhibitsticking of the tubular drill string in the well bore or damage to thedrilling means carried on the lower end of the tubular drill string.

At the present time, so far as is known to applicants, there is notavailable an arrangement which guides and protects a tubular drillstring with drilling means and removable valve means thereon into a wellbore in a desired manner to inhibit damage to the drill means on thetubular drill string being lowered, or to a surrounding tubular membersuch as the casing in the well bore, or to the wall cake on the wellbore wall.

In those instances where valve means are employed with a drill string,incorporating a drilling bit thereon, then the drill string mustincorporate a modified sub or drill collar immediately above thedrilling means on the drill string to receive the valve. This, ofcourse, increases the expense, and in some instances either duringlowering of the string into the well bore, or after it is positioned inthe well bore, the valve means which controls the flow into the drillstring, whether it is casing, tubing, or a drill string, may be aliability, particularly where it is desired to pump lost circulationmaterial down the tubular member.

The present invention is provided to overcome the above and otherdifficulties presently encountered with present float valve meansemployed for lowering tubular drill string into a well bore.

SUMMARY OF THE INVENTION An object of the present invention, therefore,is to provide a guide and protector arrangement for the lower end oftubular drill strings with drill means thereon which are to be loweredin a borehole, the guide and protector arrangement including moldedjacket means for protecting the drill means and there being fluidpassage means in the jacket means for communicating fluid between thewell bore and the interior of the drill string, and said jacket meansincorporating means for removably receiving a fill-up float valvetherein for controlling the flow of fluid between the well bore and theinterior of the drill string.

Still another object of the present invention is to provide a guide andprotector arrangement for the lower end of tubular drill strings withdrill means thereon that are to be lowered .into a well bore, the guideand protector arrangement including molded jacket means for protectingthe drill means, the jacket means including passage means therein forcommunicating fluid between the well bore and the interior of the drillstring, fluid pressure responsive means within the jacket means andcommunicating with the passage means intermediate the ends thereof,which fluid pressure responsive means is responsive to fluid pressure toaid in removing the jacket means when desired, and the jacket means,incorporating an arrangement for removably receiving valve means forcontrolling fluid flow between the well bore and the interior of thedrill string.

Still another object of the present invention is to provide anarrangement for guiding and protecting the cutting surfaces of adrilling means on the lower end of a drill pipe including molded jacketmeans for the cutting surfaces of the drilling means and includingpassage means therein for communicating fluid through the jacket meansand the drilling means to the interior of the drill pipe, and saidjacket means also in-- corporating fluid pressure responsive meanstherein to aid in removing the jacket means in response to fluidpressure for exposure of the cutting surfaces and means in the jacketmeans for receiving and retaining a fill-up float valve for controllingthe fluid flow between the borehole and the passage means in the jacketmeans.

Yet a further object of the present invention is to provide a fill-upfloat valve arrangement for a well string which may be removed from thewell string during lowering operations or at any other desired time.

Still another object of the present invention is to provide a fill-upfloat valve arrangement for a tubular member to be lowered into a wellbore which may be secured with the well string in a manner so as toeliminate the necessity of any special subs or machining of the drillstring.

Still another object of the present invention is to provide a fill-upfloat valve arrangement for a drill string which may be removed ifdesired for discharge of lost circulation material through the wellstring and into the well bore.

Another object of the present invention is to provide a combinationguide, protective device, and fill-up float valve arrangement for a wellstring wherein the float valve may be readily positioned on the wellstring and removed therefrom in the field.

Still another object of the present invention is to provide a fill-upfloat valve arrangement for a well string incorporating means to guideand protect the well string and wherein the float valve may be readilyremoved from the guide for replacement thereof when desired.

Yet a further object of thepresent invention is to provide anarrangement which positions a float valve means in advance of a drillbit and in advance of the lower end of the drill pipe or tubular memberas it is lowered into the well bore.

Yet a further object of the present invention is to provide anarrangement which positions a float valve means in advance .of a drillbit and in advance of the lower end of the drill pipe or tubular memberas it is lowered into the well bore, and which may be removed duringlowering operations or after the well string is positioned in the wellbore.

Other objects and advantages of the present invention will become morereadily apparent from a consideration of the following description anddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional viewillustrating a form of a drilling means, such as a rock or cone bit, byway of example only, secured to a drill pipe with a form of the guideand protector arrangement of the present invention employed thereon andincluding means for removably securing fill-up float valve meanstherein;

FIG. 2 is a sectional view illustrating one embodiment of a fill-upfloat valve means which may be employed with the guide and protectorarrangement illustrated in FIG. 1;

FIG. 3 is an end view on the line 3 3 of FIG. 2;

FIG. 4 illustrates another form of a fill-up float valve arrangement;

FIG. 4A illustrates yet another form of a fill-up float valvearrangement;

FIG. 5 illustrates still another valve means; and

FIG. 6 illustrates still another form of a fill-up float valve means.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Attention is first directed toFIG. 1 of the drawings wherein a form of the present invention isreferred to generally by the numeral 10. It will be noted that in FIG. 1of the drawings, the invention is illustrated in connection with adrilling bit, and more particularly wherein the drilling bit is in theform of a cone bit. However, such is for purposes of illustration only,as the present invention could be employed with any type of drillingmeans, such as, by way of example, a diamond bit, a blade bit, or othertype of drilling bit. The invention will be described in connection withFIG. 1 but, as noted, such is for purposes of illustration only.

A tubular member 11 in the form of a drill string is shown as havingsecured thereto a drilling bit 12 which, as noted in FIG. 1, is in theform of a cone bit. The bit 12 is constructed so that it incorporatesfluid passage means 14 therein for communicating fluid between the wellbore and the well string 11 in a desired manner during drillingoperations, as well as when the well string 1 l is being lowered intothe well bore-The invention incorporates the molded jacket means 15which form of a fill-up float may be formed of a suitable epoxy resinwith an aggregate such as silica sand incorporated therein, or othersuitable moldable means. The jacket means 15 may be formed in a manneras described in our copending applications Ser. No. 832,673 and Ser. No.107,786 hereinabove referred to. It may be molded in situ on the lowerend of the tubular member 11, or it may be formed in sections which thenmay then be adhered together in any suitable manner as described in saidcopending applications and then positioned on the lower end of thetubular member 1 1 as described in our copending application abovereferred to.

The jacket means 15 incorporates fluid passage means referred togenerally at 16 formed therein which communicates with the respectivepassage means 14 formed in the drilling means, or drill bit 12, asillustrated in FIG. 1 of the drawings and the well bore (not shown). Ifdesired, the jacket means 15 may also incorporate fluid pressureresponsive means referred to generally at 18 which communicates with thepassage means 16 so that the jacket means may be removed from thetubular string 11 in response to fluid pressure when desired. Such fluidpressure responsive means may comprise the surfaces 19 which intersector connect with passage means 16 and said surfaces may be formed by anysuitable means such as described in said copending applications Ser. No.832,673 and Ser. No. 107,786, or such fluid pressure responsive meansmay comprise some form of sintered or cellular type material which mayaccommodate fluid flow therethrough but which tends to restrict suchfluid flow to aid in removal of the jacket means in response to fluidpressure as will be described in greater detail.

The nose portion 20 of the jacket means 15 is illustrated as being of asuitable configuration to aid in guiding the tubular string 11 as it islowered into the well bore, so as to inhibit sticking of the well stringas the well string is lowered into the well bore, and provides a guideand protective arrangement for the lower end of the tubular string ordrill bit thereon to inhibit damage thereto by engagement withprotruding ledges in the well bore, or protruding surfaces in any casingstring which may be employed in the well bore, and to also inhibitdamage to the mud cake on the wall of the well bore.

As shown, the nose 20 may be somewhat elongated and is preferably of agenerally convex configuration to provide a smooth, streamlined surfaceto accomplish the foregoing results. The length and configuration of thenose portion 20 may vary as desired. The elongated portion of the nose20 of the jacket meanslS is provided with suitable means for removablyreceiving a fill-up float valve, a form of which is referred togenerally by the numeral 25 in FIG. 2. As shown, the jacket meansincorporates a longitudinally extending, enlarged passage 21 which maybe formed with threads 22 thereon along part of its longitudinal extent.This passage forms part of the passage means 16, and when the floatvalve is positioned therein, it is generally provided with passage meansfor communicating fluid between the well bore and interior of the wellstring in a desired manner. The upper end 23 of the passage 21communicates with the passage means 16 through the pressure responsivemeans 18 as illustrated. The fill-up float valve means 25 may be formedof any suitable material which may be readily milled or cut to aid inits removal from the well bore after it has sewed its function. Asshown, the float valve 25 incorporates a threaded exterior surface 26for engaging with the threads 22 to enable the fill-up float valve 25 tobe removably positioned within the passage 21.

It can be appreciated that other suitable means may be employed forremovably retaining the fill-up float valve means 25 within the passage21, such as, by way of example, incorporating a groove within the noseportion 20 of the jacket means and employing a snap ring to abut the end27 of the fill-up float valve means 25 and thereby retaining it inposition within the jacket means 15.

The float valve 25 incorporates a body 28 having passage means referredto generally at 30 extending longitudinally thereof. Plunger means 31are adapted to be slidably and sealably fitted within the body 28 forcontrolling flow through said body passage means 30 in response to fluidpressure acting on the plunger means. The plunger means 31 includes apassage 32 for communicating with the body passage means 30 and thereare cooperating surface means 38 and 40 on the body 28 and plunger orpiston 31, respectively, for shutting off flow through the body passagemeans 30 when the plunger is moved to a predetermined position withinthe body 28. More particularly, when the plunger 31 is moved downwardlywithin the body 28 far enough, the surface 40 on the lower end of thepassage 32 will engage the surface 38 formed on the upwardly andannularly extending projection 38a formed to close off flow temporarilyas may be desired.

When a float valve means 25 is positioned in the passage 21 of thejacket means 15 and the well string progressively lowered into the wellbore, it can be appreciated that fluid will be communicated from thewell bore into the interior of the well string 11 in a manner known tothose skilled in the art. It is desired at times to partially fill thewell string 11 as it is lowered into the well bore so as to aid infloating the well string 11 into the well bore to thereby reduce thewear and tear on the hoisting mechanism including the drawworks, brakes,and other components thereof. It can be appreciated that by regulatingthe amount of the exposed surface 31a of the plunger 31, then movementof the plunger 31 within the body 28 may be regulated to therebyregulate the fluid level of the liquid within the well string 1 1.

It is to be noted that suitable seal means may be provided between thevalve means 25 and the passage means 21, such seal means beingillustrated at 21a in FIG. 1 to inhibit leakage therebetween. Similarly,suitable seal means as illustrated at 28a and 28b are provided betweenthe body 28 and plunger 31.

In the form of the fill-up float valve means illustrated in FIG. 2, thebody 28 includes a chamber referred to generally at 280 which extendslongitudinally from one end 28d of the body 28 and terminates within thebody at a point 28e spaced from the other end 27 of the body 28. Thepassage means referred to at 30 extends from the end 27 of the body 28into the lower end of the chamber as shown in FIG. 2 of the drawings,and broadly speaking, the passage 32 also forms part of the passagemeans extending longitudinally of the body 28. The plunger means 31slidably fits within the chamber 28c, and as previously noted isprovided with seal means 28a and 28b. The chamber 280 is formed by twoconcentric bores 28f and 283, the bore 28g being of a smaller diameterthan the bore 28f and the plunger 31 is in turn suitably formed to havea portion 31b which fits within the bore 28g and a portion 310 whichfits within the bore 28f.

The seal means 280 is arranged between the plunger portion 31cand thebore 28f and the seal means 28!) is arranged between the plunger portion31b and bore 28g. The plunger means also incorporates passage means 31dextending into the bore 28f between the seal means 28a and 28b fordischarge of trapped fluid when the plunger means 31 moveslongitudinally of the body 28.

The plunger 31 is retained in position in the body 28 by suitable meanssuch as the annular groove 28h formed in the body 28 which is adapted toreceive the snap ring 36. Thus, the plunger 31 may be removed from thebody 28 to enable a plunger having either a larger or smaller passagemeans 32 therethrough to be positioned in passage 32 which, in turn,varies the amount of surface 31a exposed to the liquid entering andfilling well string 11 as it is lowered into the well bore.

In FIG. 4, the body 28 is again illustrated as having threads 26, and agroove 28h with a snap ring 36. In this instance, frangible disc means45 are illustrated as being positioned on a shoulder 28i within thechamber 28c extending longitudinally through the body 28. The disc 45 isadapted to rupture upon a predetermined pressure to establish freecommunication between the well bore and the interior of the well string11 through the valve means 25, pressure responsive means 18, and fluidpassage means 16 of the jacket means 15.

In FIG. 4A, the valve 25 is illustrated as incorporating a body 28wherein the frangible disc 45' is illustrated as being integrally formedwith the body 28a.

In FIG. 5, the valve means 25 is illustrated as again incorporatingthreads 26 for engaging it within the passage 21 of the jacket means 15and is shown as having a restricted bore or passage 46 therethrough forcommunicating fluid between the well bore and the interior of the wellstring as the well String 11 is lowered into the well bore.

In FIG. 6, the valve means 25 again incorporates threads 26 on theexterior surface of the body 28 and again includes a chamber 28c formedby two concentric bores 28f and 28g, with bore 283 being of a smallerdiameter than bore 28f. In this instance the bores 28f and 28g extendlongitudinally through the body 28. Plunger means 31 are provided toslidably fit within the bores 28f and 28g and seal means 28a areprovided between the plunger means 31 and the body 28 within the largerof the two bores, 28f.

A groove 28h is provided for receiving the snap ring 36 to aid inretaining the plunger 31 within the body 28.

thereof with the seal means 50 to close off flow through thelongitudinally extending passage means 30' in the body 28.

The particular type of fill-up float valve means employed in the presentinvention will depend upon the particular circumstances in eachinstance, such as well conditions, the rate at which it is desired tolower the well string, the viscosity'of the liquid within the well, theamount of liquid desired in the well string and other factors.

From the foregoing description, it can be seen that the presentinvention provides a guide and protector for the lower end of a wellstring to be lowered into a well bore wherein fluid passage means areprovided through the guide and protector for accommodating fluid flowtherethrough and valve means are employed to regulate the filling of thewell string during lowering operations.

Should it become desirable during lowering operations or after the wellstring is at a predetermined location within the well bore to dispensewith further use of the fill-up float valve arrangement, the jacketmeans may be removed by increasing the fluid pressure within the wellstring 11 so that the pressure response means 18 aids in removing thatportion of the jacket means which extends beyond the pressure responsivemeans. Where a drilling means is employed with the well string 11, thisexposes the cutting surfaces of the drilling means 12 for continuingdrilling operations. Since the valve is formed of material which may bereadily milled or cut up, such as plastic or the like, it may be drilledup and circulated up the well bore in a known manner.

in those instances where it is desired to employ a lost circulationmaterial as the well string is being lowered into the well bore, or whenthe well string is in position, the jacket means 15 may again be removedby increasing the hydraulic pressure within the well string 11 whereuponthe jacket means 15 is separated from the well string to expose the wellstring for free communication of lost circulation material or the liketherethrough and into the well bore.

vSince the valve 25 is removably positioned within the jacket means 15and in front of the drilling means 11 and on the lowermost end of thewell string, it may readily be removed at the well location and replacedwith a valve means 25 having a predetermined characteristic toaccomplish the desired function under the conditions at that particularwell location.

Furthermore, by providing an arrangement where the valve means is not anintegral part of the well string, special subs or special machining oftubular members such as drill strings and the like is avoided, thusgreatly reducing the cost while accomplishing the desirable benefits ofthe present invention.

If desired, the protector and guide arrangement may be removed byrotating the well string on the well bore bottom to gradually wear itaway.

The foregoing disclosure and description of the invention areillustrative and explanatory thereof, and various changes in the size,shape, and materials as well as in the details of the illustratedconstruction may be made without departing from the spirit of theinvention.

What is claimed is:

l. A bit guide and protector arrangement for a bit with fluid passagesadapted to be lowered in a borehole comprising:

a. molded jacket means for the bit cutting surfaces, said jacket meansincluding passage means therein for communicating fluid through saidjacket means to the bit;

. fluid pressure responsive means within said jacket means andcommunicating with the passage means intermediate the ends thereof, saidfluid pressure responsive means being responsive to fluid pressure toaid in removing saidjacket means for exposure of the bit cuttingsurfaces; and v fill-up float valve means positioned in said jacketmeans for controlling the fluid flow between the borehole and thepassage means in said jacket means.

2. The invention of claim 1 wherein cooperating means are provided onsaid jacket means and said float valve to enable said float valve to bereadily engaged with and removed from position in said jacket means.

3. The invention of claim 1 wherein said float valve comprises:

a. a body having passage means extending longitudinally thereof;

b. plunger means slidably and sealably fitting in said body forcontrolling flow through said body passage means in response to fluidpressure acting on said plunger means; and Y c. cooperating surfacemeans on said body and plunger means for shutting off flow through saidpassage means when said plunger is moved to a predetermined position insaid body.

4. The invention of claim 3 including snap ring means fitting in agroove in said body for removably retaining said plunger means withinsaid body.

5. The invention of claim 2 wherein said cooperating means comprisescooperating threaded surfaces on said jacket means and float valve.

6. The invention of claim 1 wherein said float valve includes passagemeans therethrough, and frangible disc means closing off said passagemeans but breakable when the pressure thereon reaches a predeterminedamount to open the passage means to fluid flow.

7. The invention of claim 1 wherein said jacket means is formed of aplurality of sections, and means for bonding said sections togetherafter they are positioned on the bit.

8. The invention of claim 1 wherein said float valve comprises:

a. a body;

b. said body having a chamber therein extending longitudinally from oneend of said body and terminating within said body spaced from the otherend;

c. said body having passage means extending from said other end of saidbody into the chamber;

d. plunger means for slidably fitting in the chamber of said body;

e. said means for sealing between said plunger and f. there beingpassage means extending longitudinally through said plunger means; and

g. means in said body cooperating with said plunger means to close offthe passage means in said body and plunger means when said plunger movesa predetermined distance longitudinally of said body.

9. The invention of claim 8 wherein said chamber comprises twoconcentric bores, one of which is of a smaller diameter than the otherand said plunger means extends within both of the bores.

10. The invention of claim 9 wherein there are seal means between saidbody and plunger means in both of the bores.

11. The invention of claim 10 including snap ring means for fitting in agroove in said body for removably retaining said plunger means withinsaid body.

12. The invention of claim 1 wherein said float valve comprises a body,cooperating means on said body and jacket means for removablypositioning said body within said jacket means and said body havingpassage means therethrough for communicating with the passage means insaid jacket means.

13. The invention of claim 1 wherein said float valve comprises:

a. body means;

b. said body having a chamber therein extending longitudinally from oneend of said body to the other end, the chamber comprising two concentricbores, one of which is of a smaller diameter than the other;

0. plunger means for slidably fitting within both of the bores;

(1. seal means between said plunger means and body for slidably andsealably receiving the plunger within the larger of the two bores;

e. means within the larger of the two concentric bores for retainingsaid plunger within said body;

f. there being passage means in said body, one end of which communicateswith the larger of the two bores on one side of said retaining means andwith the smaller of the two bores at its other end; and

g. seal means carried by said body within the smaller bore between saidother passage end and said other body end whereby a predeterminedmovement of said plunger means within said body means closes off thepassage in said body.

14. The invention of claim 10 wherein said plunger means includes portmeans extending therethrough between said seal means for discharge oftrapped fluid when said plunger moves longitudinally of said body.

15. A guide and protector arrangement for the lower end of devices suchas tubular members andthe like which are to be lowered in a boreholecomprising:

a. molded jacket means for covering the lower end of the devices, saidjacket means including passage means therein for communicating fluidbetween the well bore and the interior of the devices;

. fluid pressure responsive means within said jacket means andcommunicating with the passage means intermediate the ends thereof, saidfluid pressure responsive means being responsive to fluid pressure toaid in removing said jacket means for exposure of the lower end of thedevice; and

. fill-up float valve means positioned in said jacket means forcontrolling the fluid flow between the borehole and the remainder of thepassage means in said jacket means.

1. A bit guide and protector arrangement for a bit with fluid passagesadapted to be lowered in a borehole comprising: a. molded jacket meansfor the bit cutting surfaces, said jacket means including passage meanstherein for communicating fluid through said jacket means to the bit; b.fluid pressure responsive means within said jacket means andcommunicating with the passage means intermediate the ends thereof, saidfluid pressure responsive means being responsive to fluid pressure toaid in removing said jacket means for exposure of the bit cuttingsurfaces; and c. fill-up float valve means positioned in said jacketmeans for controlling the fluid flow between the borehole and thepassage means in said jacket means.
 2. The invention of claim 1 whereincooperating means are provided on said jacket means and said float valveto enable said float valve to be readily engaged with and removed fromposition in said jacket means.
 3. The invention of claim 1 wherein saidfloat valve comprises: a. a body having passage means extendinglongitudinally thereof; b. plunger means slidably and sealably fittingin said body for controlling flow through said body passage means inresponse to fluid pressure acting on said plunger means; and c.cooperating surface means on said body and plunger means for shuttingoff flow through said passage means when said plunger is moved to apredetermined position in said body.
 4. The invention of claim 3including snap ring means fitting in a groove in said body for removablyretaining said plunger means within said body.
 5. The invention of claim2 wherein said cooperating means comprises cooperating threaded surfaceson said jacket means and float valve.
 6. The invention of claim 1wherein said float valve includes passage means therethrough, andfrangible disc means closing off said passage means but breakable whenthe pressure thereon reaches a predetermined amount to open the passagemeans to fluid flow.
 7. The invention of claim 1 wherein said jacketmeans is formed of a plurality of sections, and means for bonding saidsections together after they are positioned on the bit.
 8. The inventionof claim 1 wherein said float valve comprises: a. a body; b. said bodyhaving a chamber therein extending longitudinally from one end of saidbody and terminating within said body spaced from the other end; c. saidbody having passage means extending from said other end of said bodyinto the chamber; d. plunger means for slidably fitting in the chamberof said body; e. said means for sealing between said plunger and body;f. there being passage means extending longitudinally through saidplunger means; and g. means in said body cooperating with said plungermeans to close off the passage means in said body and plunger means whensaid plunger moves a predetermined distance longitudinally of said body.9. The invention of claim 8 wherein said chamber comprises twoconcentric bores, one of which is of a smaller diameter than the otherand said plunger means extends within both of the bores.
 10. Theinvention of claim 9 wherein there are seal means between said body andplunger means in both of the bores.
 11. The invention of claim 10including snap ring means for fitting in a groove in said body forremovably retaining said plunger means within said body.
 12. THeinvention of claim 1 wherein said float valve comprises a body,cooperating means on said body and jacket means for removablypositioning said body within said jacket means and said body havingpassage means therethrough for communicating with the passage means insaid jacket means.
 13. The invention of claim 1 wherein said float valvecomprises: a. body means; b. said body having a chamber thereinextending longitudinally from one end of said body to the other end, thechamber comprising two concentric bores, one of which is of a smallerdiameter than the other; c. plunger means for slidably fitting withinboth of the bores; d. seal means between said plunger means and body forslidably and sealably receiving the plunger within the larger of the twobores; e. means within the larger of the two concentric bores forretaining said plunger within said body; f. there being passage means insaid body, one end of which communicates with the larger of the twobores on one side of said retaining means and with the smaller of thetwo bores at its other end; and g. seal means carried by said bodywithin the smaller bore between said other passage end and said otherbody end whereby a predetermined movement of said plunger means withinsaid body means closes off the passage in said body.
 14. The inventionof claim 10 wherein said plunger means includes port means extendingtherethrough between said seal means for discharge of trapped fluid whensaid plunger moves longitudinally of said body.
 15. A guide andprotector arrangement for the lower end of devices such as tubularmembers and the like which are to be lowered in a borehole comprising:a. molded jacket means for covering the lower end of the devices, saidjacket means including passage means therein for communicating fluidbetween the well bore and the interior of the devices; b. fluid pressureresponsive means within said jacket means and communicating with thepassage means intermediate the ends thereof, said fluid pressureresponsive means being responsive to fluid pressure to aid in removingsaid jacket means for exposure of the lower end of the device; and c.fill-up float valve means positioned in said jacket means forcontrolling the fluid flow between the borehole and the remainder of thepassage means in said jacket means.